Sorry for resurrecting an old thread, but the answers you're looking for on the Powers side are at http://revwarapps.org/r8412.pdf . See footnotes in which Zilla (widow of William) exercises power of attorney along with William's sisters, Experience and Elizabeth.

William & Zilla's daughter Elizabeth married Riley Wilson (http://www.wikitree.com/wiki/Wilson-21942), my third great-grandfather.